This study of 176 university students tested a single-session explanatory feedback intervention (EFI), derived from the perfectionism coping processes model. Participants with higher self-critical perfectionism completed daily measures of stress appraisals, coping, and affect for 7 days. A randomized control design was used to compare an EFI condition with a waitlist control condition over 4 weeks with individualized feedback delivered one-on-one by student trainees in-person or remotely through videoconferencing. The feasibility of the individualized analyses of each participant's daily data was supported by identifying daily trigger patterns, maintenance tendencies, strengths, common triggers, and best targets for reducing negative mood and increasing positive mood across several stressors for each participant. Participant ratings indicated that the comprehensive feedback was coherent and functional. Participants in the EFI condition, compared to those in the control condition, reported increases in empowerment, coping self-efficacy, and problem-focused coping, as well as decreases in depressive and anxious symptoms. Between-group effect sizes were moderate-to-large. There were reliable improvements in empowerment and depressive symptoms for 56% and 36%, respectively, of participants in the EFI condition. These findings demonstrate the broad applicability, conceptual utility, and effectiveness of the EFI for self-critical perfectionistic individuals. (PsycInfo Database Record (c) 2023 APA, all rights reserved).